The present invention relates to a hot water supply device, and in particular relates to a hot water supply device that is endowed with a function of deciding whether or not lime scale has built up within the heat exchange tubing of a heat exchanger and has caused clogging.
From the past, hot water supply devices of various types employing heat sources of various types, such as gas-powered hot water supply devices, electricity-powered hot water supply devices, oil-powered hot water supply devices, and so on, have been widespread for general household use. In particular, a typical such gas-powered hot water supply device incorporates a blower fan that sucks in air from the external atmosphere for combustion, a burner unit that mixes the air with fuel gas and combusts the resulting mixture, a heat exchanger that exchanges heat between the resulting high temperature combustion gases and water flowing in heat exchange tubing and thereby heats up the water, an exhaust pipe for discharging the exhaust after the above heat exchange to the external atmosphere, and so on.
Usually a fin-and-tube type heat exchanger that includes the above described heat exchange tubing and a plurality of fins that are fixed to the heat exchange tubing for conducting heat exchange with the combustion gases is applied as the heat exchanger described above, with either stainless steel or copper being normally used as the material for the heat exchange tubing and the fins.
However, if a mains water whose hardness is high is used for the fresh water that is supplied to the heat exchanger, then lime scale is apt to be created by combination between calcium or magnesium or the like contained in the mains water and ions of carbonic acid or sulfuric acid, and there is a problem that clogging by scale may occur due to the lime scale undesirably building up within the heat exchange tubing of the heat exchanger, in which case the efficiency of heat exchange in the heat exchanger will deteriorate. Moreover, when the hot water supply device is used over the long term, fin clogging may take place due to soot or the like adhering to the fins, and this also may cause a problem with deterioration of the heat exchange efficiency of the heat exchanger.
There is a fear of damage to the heat exchanger if usage of the hot water supply device continues in the state in which the clogging with scale or fin clogging has occurred, and accordingly it is necessary to perform maintenance in order to eliminate the lime scale or the soot if an anomaly such as clogging with scale or fin clogging has taken place. Due to this, in the past, hot water supply devices have been endowed with a function of detecting an anomaly such as clogging with lime scale or the like.
Here, as prior art documents, the following four publications may be mentioned:
Patent Document #1: JP Patent Publication 4854020.
Patent Document #2: JP Laid Open Pat. Publication 2003-25461.
Patent Document #3: JP Laid Open Pat. Publication 2013-160488.
Patent Document #4: JP Laid Open Pat. Publication 2008-215657.
For example, with the devices described in Patent Documents #1 through #3, a technique is disclosed of determining that clogging with scale has taken place on the basis of heat rise an increase of the temperature of the warm water after shutoff of combustion. Moreover, with the device for heating to water described in Patent Document #4, a technique is disclosed in which the level of combustion is forcibly reduced when it is detected during combustion operation that the efficiency of heat exchange has dropped, and after this reduction the detected heat exchange efficiency is compared with a standard efficiency, and a determination is made as to whether the cause of the deterioration of heat exchange efficiency is clogging with lime scale or clogging of the fins.
However, if anomaly determination is performed on the basis of increase of the temperature of the remaining warm water that takes place due to heat rise after shutoff of combustion, as in the case of Patent Documents #1 through #3, then it is not possible to determine the cause of deterioration of heat efficiency accurately, i.e. to determine whether this deterioration has occurred due to poor heat exchange because of clogging with lime scale or due to poor heat exchange because of fin clogging, and accordingly, when maintenance is performed or countermeasures are instituted, there is a fear that labor may be wastefully employed. Furthermore there is also the problem that, if the amount of combustion just before combustion is stopped is low and the immediate hot water system is operating, then it is not possible to take advantage of elevation of the temperature of the remaining warm water due to heat rise after shutoff for the determination of an anomaly.
Moreover, although, in the case of the device for heating water described in Patent Document #4, a determination is performed during combustion operation for specifying whether the cause of poor efficiency is clogging with lime scale or fin clogging, since the amount of combustion is forcibly reduced in order to perform specification of the cause of poor efficiency during combustion operation with the technique of Patent Document #4 even when the operational state of supplying hot water is normal, accordingly the problem arises that the hot water supply amount and/or the hot water supply temperature may undesirably fluctuate, which would be contrary to the intentions of the user.
The object of the present invention is to provide a hot water supply device that is capable of reliably determining clogging by scale with a simple method.